This type of automation system is known for example from WO 2005/015330 A. It relates to a system and method for identifying passive automation components, especially sensors, actuators and power components. The automation device features a reader for reading out data stored on an RFID chip which is intended for use in the control unit.
Furthermore an automation system is known from numerous applications, which is used for performing a control task or which takes over the regulation of a process. It reads in the values of sensors and operating elements and processes these with internal states into output values for actuators. A modern automation system consists to a significant extent of software, so as to enable it to be adapted by users to suit their particular tasks.
The sensors convert physical variables such as pressure, temperature, brightness etc. into electrical values. The actuators in their turn convert electrical energy into forces, heat, light etc. The automation system consists of a processing unit and many modules to which the sensors and actuators are connected.
The number of different sensors and actuators is very large. So that a separate module does not have to be developed for each type of sensor or actuator, they are grouped together in accordance with their characteristics. For example most temperature sensors are resistors. To measure a temperature, a temperature-dependent resistor is measured. The resistance value can then be converted into a temperature value. The conversion can be undertaken in the module, but this means that the module must know the exact type of temperature sensor. The sensor or actuator type is notified to the module by means of software written for the purpose: The hardware configuration.
The hardware configuration has two primary tasks. It adapts the modules to the sensors and actuators and makes the addresses to be used available to the processing unit for each module. In addition it can check whether the parameterized modules are also really present. However only in few cases is a check made as to whether the correct sensor or actuator is connected. Although it is possible to check with the simpler sensors, such as the NTC thermistors or PTC thermistors used for temperature measurement, whether a resistor is connected at all but its temperature curve could be determined by a measurement curve. The same also applies to actuators. Whether a 10 W motor or a 10 kW motor is connected to the output has no part to play for the controller, since both are activated with a voltage of 0 V to 10 V. This voltage is converted by a regulator directly on the motor into the desired power. There are also actuators which are activated with currents of 4 mA to 20 mA. Confusing these two output types can have fatal consequences.
The controller cannot check whether the correct sensor or actuator is connected. The hardware configuration is tedious and error-prone. Every sensor and actuator has different characteristics. The manufacturer of sensors must work very precisely to keep within the desired tolerances. To this end manufacturing is followed by a calibration, i.e. fine tuning is carried out with a laser. Precise linear sensors are thus very expensive.
A higher accuracy can be obtained if the characteristic curves of the sensors error-prone. For each sensor a data sheet with the actual characteristic-curve must be supplied and this then entered into the automation system. Even if this information is entered electronically, using a diskette for example, errors cannot be avoided. In any event this process must be repeated if components are replaced, e.g. if spares are provided.